The present embodiments include an ink jet print head front face or nozzle plate having a textured superoleophobic surface that prevents undesirable drooling, wetting and/or adhesion of the ink on the print head. The textured surface includes a rim formed around the nozzle. Also described are methods for forming the textured superoleophobic ink jet print head front face or nozzle plate from silicon having the textured, oleophobic surface. The methods include using superoleophobic surfaces prepared using photolithography to create a textured pattern in the silicon. In specific embodiments, the flexible, superoleophobic device made is used as a front face or nozzle plate surface for a microelectromechanical system (MEMSJet) based drop ejector print head.
Fluid ink jet systems typically include one or more printheads having a plurality of ink jets from which drops of fluid are ejected towards a recording medium. The ink jets of a printhead receive ink from an ink supply chamber or manifold in the printhead which, in turn, receives ink from a source, such as a melted ink reservoir or an ink cartridge. Each ink jet includes a channel having one end in fluid communication with the ink supply manifold. The other end of the ink channel has an orifice or nozzle for ejecting drops of ink. The nozzles of the ink jets may be formed in an aperture or nozzle plate that has openings corresponding to the nozzles of the ink jets. During operation, drop ejecting signals activate actuators in the ink jets to expel drops of fluid from the ink jet nozzles onto the recording medium. By selectively activating the actuators of the ink jets to eject drops as the recording medium and/or printhead assembly are moved relative to one another, the deposited drops can be precisely patterned to form particular text and graphic images on the recording medium. MEMSJet drop ejectors consist of an air chamber under an ink chamber, with a flexible membrane in-between. Voltage is applied to an electrode inside the air chamber, attracting the grounded flexible membrane downward, increasing the volume of the ink chamber and thus lowering its pressure. This causes ink to flow into the ink chamber from the ink reservoir. The electrode is then grounded and the membrane's restoring force propels it upward, creating a pressure spike in the ink cavity that ejects a drop from the nozzle. An example of a full width array printhead is described in U.S. Patent Publication 20090046125, which is hereby incorporated by reference herein in its entirety. An example of an ultra-violet curable gel ink which can be jetted in such a printhead is described in U.S. Patent Publication 20070123606, which is hereby incorporated by reference herein in its entirety. An example of a solid ink which can be jetted in such a printhead is the Xerox ColorQube™ cyan solid ink available from Xerox Corporation. U.S. Pat. No. 5,867,189, which is hereby incorporated by reference herein in its entirety, describes an ink jet print head including an ink ejecting component which incorporates an electropolished ink-contacting or orifice surface on the outlet side of the printhead.
One difficulty faced by fluid ink jet systems is wetting, drooling or flooding of inks onto the printhead front face. Such contamination of the printhead front face can cause or contribute to blocking of the ink jet nozzles and channels, which alone or in combination with the wetted, contaminated front face, can cause or contribute to non-firing or missing drops, undersized or otherwise wrong-sized drops, satellites, or misdirected drops on the recording medium and thus result in degraded print quality. Current printhead front face coatings are typically coated with a hydrophobic coating, for example, a sputtered polytetrafluoroethylene coating. However, the ink as an organic matter behaves differently than water, and can demonstrate ink-philic characteristics with the front face surface. When the printhead is tilted, the UV gel ink at a temperature of about 75° C. (75° C. being a typical jetting temperature for UV gel ink) and the solid ink at a temperature of about 105° C. (105° C. being a typical jetting temperature for solid ink) do not readily slide on the printhead front face surface. Rather, these inks flow along the printhead front face and leave an ink film or residue on the printhead which can interfere with jetting. For this reason, the front faces of UV and solid ink printheads are prone to be contaminated by UV and solid inks. In some cases, the contaminated printhead can be refreshed or cleaned with a maintenance unit. However, such an approach introduces system complexity, hardware cost, and sometimes reliability issues. Further, the front face coatings sometimes have trouble withstanding the chemistry of the ink, and repeated wiping from a maintenance wiper blade often clears away much of the coating, resulting in more severe ink wetting and flowing on the nozzle plate surface, leaving residues. Additionally, full-width array printheads made up of a series of subunits must be potted to fill in the cracks between units, in order to avoid damage to the wiper blade from the edges of the subunits. This can make reworking of the print heads very difficult because the potting must be removed and reapplied after the new subunit is inserted.
There remains a need for an ink jet print head and method for preparing same wherein the front face or nozzle plate exhibits superoleophobic characteristics alone or in combination with superhydrophobic characteristics. Further, while currently available coatings for ink jet printhead front faces are suitable for their intended purposes, a need remains for an improved printhead front face design that reduces or eliminates wetting, drooling, flooding, or contamination of UV or solid ink over the printhead front face. There further remains a need for an improved printhead front face design that is ink phobic, that is, oleophobic, and robust to withstand maintenance procedures such as wiping of the printhead front face. There further remains a need for an improved printhead front face design that is superoleophobic and, in embodiments, that is both superoleophobic and superhydrophobic. There further remains a need for an improved printhead that is easily cleaned or that is self-cleaning, thereby eliminating hardware complexity, such as the need for a maintenance unit, reducing run cost and improving system reliability.
The appropriate components and process aspects of the each of the foregoing U.S. Patents and Patent Publications may be selected for the present disclosure in embodiments thereof. Further, throughout this application, various publications, patents, and published patent applications are referred to by an identifying citation. The disclosures of the publications, patents, and published patent applications referenced in this application are hereby incorporated by reference into the present disclosure to more fully describe the state of the art to which this invention pertains.